THE MASSACHUSETTS CONTACT tracing effort, which scaled back its workforce dramatically this summer as the spread of COVID-19 subsided, is ramping up again.

The nonprofit Partners in Health, which works with local boards of health across the state to track down those who have been infected with the coronavirus and those they have come in contact with, is operating much like an accordion, contracting in late June and July as cases diminished and now expanding again.

Jason Lefferts, a spokesman for the Massachusetts Connector, which hired Partners in Health, said in an email that the contact-tracing workforce is expanding now because of an “expected ramp-up in cases, particularly as we work with colleges and universities.”

The state’s COVID-19 benchmarks are a mixed bag of data points suggesting the virus is ebbing across most of the state while spreading in more than 50 individual communities. The expansion at Partners in Health suggests those charged with combatting the virus are expecting some resurgence this fall.

Lefferts said Partners in Health added 100 employees in the latter half of August, bringing the total to 661 as of September 1. Another 100 will be added over the next several weeks, Lefferts said.

Those numbers are still well below the level of the contact tracing effort during the coronavirus surge. The numbers topped 1,300 at one point, fell back to 1,212 in mid-June, and then were slashed to around 550 through a combination of voluntary departures and then layoffs.

Partners in Health has a contract with the state that runs through the end of the year with an option to extend it through March. Lefferts said no decision has been made on the extension yet, but sources say it looks like the contract option will be picked up.

The recent employee expansion was not entirely unexpected. When employees were cut earlier this summer, Lefferts said the “goal remains to contact every person who tests positive for COVID-19 and their close contacts. But as the number of cases and close contacts in the Commonwealth continues to trend downward, the CTC [the abbreviation for the Contract Tracing Collaborative, the combination of local boards of health and Partners in Health] has determined its workforce can be reduced at this time and still meet the tracing needs of the Commonwealth. If there is an increase in cases, the CTC has the infrastructure in place to quickly scale back up its staffing operation to meet demand.”

The ramp-up in employment at Partners in Health coincides with an expansion of the number of communities at high risk for COVID-19. At a press conference in Medford on Thursday, Gov. Charlie Baker said the expansion from 8 to 13 communities is something to keep an eye on but not overly concerning. He said some of the new communities identified as high risk probably had isolated events that vaulted them into the high-risk group. Chatham, which had an outbreak at a restaurant, and Dedham, where young people got together to watch a Boston Bruins hockey game, are two examples.

Baker said if those communities remain on the list three weeks from now, that would be a cause for concern. The one community in the high-risk group that has seen its numbers rise fairly dramatically over the last three weeks is Lawrence, where the number of cases per 100,000 people over the previous two weeks rose from 8.5 on August 12 to 20.5 on Wednesday. Anything above 8 puts a community in the high-risk group.